It was a bold plan, but quite a feasible plan after all. Taking advantage of the undertow that snatched up every loosened particle of sand and scurried it away, Jay proposed to do a little excavating in the neighborhood of the U-boat and leave it to the currents themselves to exhume the lost ship--at least to free it far enough for the divers to get inside and salvage the plans so much wanted by the U. S. Government. And now Jay was ready to be off. His new "vacuum cleaner" was ready and the air pump working smoothly. "Good luck to you," called out Captain Austin as Dick prepared to clamp on his chum's helmet. The youth smiled and in a moment shuffled to the side and was over and gone deep down into the embrace of the green sea, his air hose fastened at his belt. Pretty soon he was on bottom and groping his way along from hummock to hummock, now stumbling and now lifted by the whirling currents. Presently he came upon the periscope pole and the mushroom anchor he had left below the previous night. But now the anchor sat deep down in a wide depression that opened out of the floor of the sea like the crater of a volcano. "Bless my soul if that undertow hasn't been working for me all night," he observed while noting that the sand had been scooped out in huge quantities in every direction radiating from the periscope pole. Which made it that much easier for the submarine excavator. The digging, of course, but not the actual work; for the deadly currents were dragging the youth to and fro until he reeled and tottered like a drunken man. But Jay had come prepared so that he would not again be subjected to the terrific mauling he had received before. This time he had piled on lead until he was heavily weighted down. A canvas belt, slung from hips to armpits, with pockets, held close to fifty pounds of metal. In addition he had fastened around each ankle a bag containing another twenty-five pounds. As he prepared to swing his air hose into action Jay found the sea clutching and tearing viciously at his own air and signal lines and he made sure that they were intact and working perfectly before he gave the signal for the air to be turned into the "spray" line that he carried. At last the youth was ready for his experiment. Jay had no idea how his plan would turn out, for, while he had heard of this kind of work and knew of its practicability, he had never tried it out for himself. It was his purpose to start the sand shifting in the belief that once the movement was under way the freakish undertow and cross-currents would come to his assistance and facilitate the task of unearthing the U-boat. "Here goes," he cried as he sat down on the sandy bottom and, holding the nozzle of the hose away from him at an oblique angle of forty degrees, turned on the air full force.